Abstracts

The Ontario Geological Survey (OGS) began mapping both the overburden and shallow
and deeper bedrock potable groundwater resources along the Niagara Escarpment in 2009.
The main goal was to establish a 3D geologic model that could be used to delineate and
predict locations of new groundwater resources for populations in key growth areas within
the Escarpment region. The timing of the regional bedrock aquifer mapping initiative
coincided with the Town of Shelburne retaining a consulting team to conduct a hydrogeological
study to find additional groundwater supplies in bedrock to augment four existing
wells, in order to meet future increased population and industry demands. The consultants
were to review all existing hydrogeological data and select favourable areas within a 5km
perimeter of the town boundary.
The Shelburne groundwater exploration study also coincided with anticipated changes
in the Ontario Drinking Water Standards for Arsenic levels – some of the existing bedrock
wells, which ended in the interface aquifer contact zone, had produced As levels that
would exceed the new standard. OGS bedrock geochemistry, petrology and SEM studies
had revealed that As was naturally occurring and concentrated in microbially-precipitated
framboidal pyrites in some of the rock formations of the Lockport Group – the main
cliff-forming package of carbonates that hosts the potable groundwater flow zones along
the Niagara Escarpment. OGS staff presented current knowledge of the regional 3D bedrock
model and groundwater flow zones to the Town and consultants in December 2009.
Extrapolation of the 3D geologic model into the Melancthon-Shelburne areas, along with
renewed regional mapping that indicated major changes were needed to describe the bedrock
stratigraphy of the area, resulted in the drilling of two cored holes to the regional
bedrock aquitard – Cabot Head Formation (>95m depth).
Subsequent core analysis, down-hole camera and geophysical tests, packer pumping tests
and FLUTe profiling indicated potential deeper groundwater flow zones in the Goat
Island and Gasport formations, with a total local thickness of 40m. A larger diameter
water well was drilled and tested next to the more promising OGS-FLUTe-instrumented
monitoring well, and confirmed a supply that is more than double the capacity the Town
was expecting and with low As levels. Both a Municipal Class EA and Federal EA have
since been completed and approved. The Town is expecting to bring the new water supply
of more than 1600m 3 /day on-line in 2015.
137 - Regional groundwater resources assessment in the
Chaudière-Appalaches region, Québec, Canada
Jean-Marc Ballard 1 , Marc-André Carrier 1 , Harold Vigneault 1 , Guillaume
Légaré-Couture 1 , Michel Parent 2 , Laureline Berthot 1 Châtelaine Beaudry 1 , Marc
Laurencelle 1 , Xavier Malet 1 , Annie Therrien 1 , & René Lefebvre 1
1
INRS, Centre Eau Terre Environnement, Québec City, Québec, Canada
2
Natural Resources Canada, Geological Survey of Canada, Québec City, Québec, Canada
A groundwater resources assessment was carried out in the 15 600 km 2 Chaudière-Appalaches
region extending south from the St. Lawrence River to the USA border. Data
compilation extracted more than 20 000 well records from the governmental well database.
174 IAH-CNC 2015 WATERLOO CONFERENCE